This invention relates to a method of manufacturing a stable solution containing bisphenolic stillbottoms. This invention also relates to phenolic compositions that are manufactured using solutions of bisphenolic stillbottoms. This invention further relates to phenolic compositions that are useful in the manufacture of laminates and paper products.
Bisphenol A stillbottoms, as one example of bisphenolic stillbottoms known in the art, are produced by dehydrocondensing phenol and acetone in the presence of a strong acid catalyst. When bisphenol A is separated from the reaction mixture by distillation, for example, or by other purification methods, there is a material remaining that has been generally described in the art as a bisphenol stillbottom. Consistent with the use of the term in the art, hereinafter, the term bisphenol stillbottoms refers to that material separated during the preparation of bisphenol that is not purified bisphenol. Thus, bisphenol A stillbottoms may contain some bisphenol A. The bisphenol A stillbottom typically contains, in predominant proportions, other phenol-acetone reaction products. Dihydroxydiphenylpropane isomers and chromane compounds are typically present in lesser amounts.
The reuse of bisphenolic stillbottoms is generally quite limited. Bisphenolic stillbottoms are a solid at room temperature and typically must be kept in a molten state, or processed into a small particle such as a flake or powder, if the stillbottoms are to be further used in most manufacturing processes. Molten stillbottoms are subject to degrading oxidation Therefore, the chemical composition of the stillbottoms will change as function of the length of storage time in the molten state. As a result of this changing chemical composition, products made using molten stillbottoms may have unpredictable properties. The processing of stillbottoms into an intermediate form, such as a flake or powder, adds significant cost to products made using this intermediate form and a flake or powder may sinter. Therefore, typically, bisphenolic stillbottoms are incinerated for disposal.
The use of bisphenolic stillbottoms in phenolic resin compositions has until now been limited. Not surprisingly, because phenolic resins are typically condensed from aqueous solutions, the insolubility of bisphenoic stillbottoms generally makes their use prone to problems. In one prior art process, for example, bisphenol A stillbottoms must be further refined before they are useable in the synthesis of a novolac resin. In this process, bisphenol A stillbottom are further processed, at extreme temperatures, reduced pressures and in the presence of an alkaline catalyst, to recover phenol and isopropenyl phenol. A residue remains after such processing and this residue is said to be useful in the manufacture of novolac resins.
The use of bisphenols in phenolic resin synthesis in the prior art is surprisingly limited. As described above with respect to bisphenol stillbottoms, the relative insolubility of bisphenolic compounds generally makes their use prone to problems. For example, in one prior art composition, alkylidenepolyphenols, together with a trifunctional phenol and formaldehyde, are used in the synthesis of resoles. However, as the prior art provides, the timing of the addition of the alkylidenepolyphenol is critical. The alkylidenepolyphenol can be added neither at the start of the synthesis nor near the end of the synthesis, but must be added at some mid-point in the reaction sequence. One prior art process describes a resin that is the reaction of product of formaldehyde and bisphenol A. However, as the prior art teaches, it is essential to maintain a very narrow mole ratio of formaldehyde to bisphenol A. Resins of this type have limited application as leveling compounds or metal coating compounds.
The preparation of aqueous solutions of bisphenolic stillbottoms, let alone the use of these aqueous solutions in the manufacture of resins, until now has been unknown in the art. It has been generally concluded in the prior art that bisphenolic stillbottoms do not form stable aqueous solutions. It has been taught in the prior art that bisphenol A, for example, forms a two-phase system with hot water. It is known that molten bisphenol A forms a two-phase system with water at temperatures even as high as 85xc2x0 C. to 100xc2x0 C. In fact, it has long been known in the art that water washing of phenolic mixtures is one means to recover a relatively pure phenol product. The water will dissolve inorganic salts and acid impurities, while the phenolic product readily separates from the aqueous solution.
The development of methods that would allow reuse of bisphenolic stillbottoms have understandably been the object of few prior art attempts. One prior art process provides an aqueous suspension of ultrafine bisphenol particles. Strongly alkaline compounds are used in the preparation of such a suspension. This suspension is used in the preparation of polycarbonates. Yet another prior art process uses strongly alkaline compounds, such as sodium hydroxide, to provide for the dissolution of bisphenol A in hot water. In this prior art process, purified bisphenol A may be recovered from a bisphenolic mixture. Fractions of the bisphenolic mixture will dissolve in the hot water in increasing amounts as the amount of sodium hydroxide is increased. Purified insoluble bisphenol A is recovered by separation from the liquid portion that contains the soluble fractions. Still another prior art process employs a co-solvent, such as an alcohol, to provide for the dissolution of diphenols in water. In this prior art process bisphenol A is said to dissolve in a water/alcohol solution that has been heated to reflux. This process is said to be useful in the purification of bisphenol A.
Each of the prior art processes has disadvantages. A heterogeneous two-phase system of bisphenolic stillbottoms and water is an impractical composition both for the storage of bisphenolic stillbottoms and the use of the stillbottoms in the synthesis of resins. Likewise, the use of strongly alkaline materials or co-solvents adulterates the bisphenolic stillbottoms thus limiting the further use of the modified stillbottoms. The use of molten bisphenolic stillbottoms can result in degradation of the bisphenolic stillbottoms thus affecting the properties of resins made using such stillbottoms. Pre-processing the bisphenolic stillbottoms into a flake or powder is costly. Furthermore, flakes or powders must be re-dissolved during the synthesis of a resin in order for the flake or resin to participate in the synthesis. The re-dissolution presents yet an additional energy requirement. Purification of the bisphenolic stillbottoms to another form is an energy intensive process that changes the chemical composition of the bisphenolic stillbottoms, thus further limiting the utility of the modified form.
It would therefore be advantageous to have a stable aqueous solution of bisphenolic stillbottoms thus obviating the need to store bisphenolic stillbottoms in a molten state or to further process bisphenolic stillbottoms into a flake or powder form. It would also be an advantage to have a phenolic resin composition that included in the manufacture of the phenolic resin the use of a stable aqueous solution of bisphenolic stillbottoms. It would be a further advantage to have a process for using bisphenolic stillbottoms in the synthesis of phenolic resins that did not require refinement of the bisphenolic stillbottoms into another chemical form.
The preparation of laminates and resin-impregnated papers using phenolic resins is also known in the art. The resins used in such preparations range from low molecular weight resins having a high tolerance for water to high molecular weight resins having a low tolerance for water.
The preparation of laminates and resin saturated papers using phenolic resins based on the prior art has attendant disadvantages. Low molecular weight resins are typically prepared by using a high phenol to formaldehyde ratio, or, in the alternative, a low formaldehyde to phenol ratio. Such resins typically contain a high free phenol content. These resins, accordingly, exhibit high emissions when subjected to the elevated temperatures realized in the manufacture of laminates.
It would therefore be an advantage to have a low cost process for producing low molecular weight resins that also contain low amounts of residual free phenol. It would be a further advantage to have a product of such a process.
The present invention provides a stable aqueous solution of bisphenolic stillbottoms. The present invention also provides a resole composition that includes in the manufacture of the resin the use of a stable aqueous solution of bisphenolic stillbottoms. The present invention further provides a process for using bisphenolic stillbottoms in the synthesis of phenolic resins that does not require refinement of the bisphenolic stillbottom into another chemical form.
The present invention provides a low molecular weight phenolic resin that exhibits improved paper saturation and reduced phenol emissions during treating when compared to the prior art. The present invention also provides a method for making low molecular weight phenolic resins that provide improved paper saturation and reduced phenol emissions during treating when compared to the prior art.
The present invention further provides a resin, and a method for making such a resin, that results in a paper laminate that can provide improved flexibility when compared to the prior art.
According to one embodiment of the present invention, a single-phase composition of bisphenolic stillbottoms is prepared by mixing water and bisphenolic stillbottoms together under controlled conditions. Surprisingly, it has been determined that when water is mixed with molten bisphenolic stillbottoms, under reflux conditions a stable composition results. Such a composition is a single-phase solution at temperatures as low as 75xc2x0 C., and a single-phase composition that is a semi-solid ranging from a wax-like to a tar-like consistency at room temperature. The single-phase semi-solid can then be reheated to form a single phase liquid.
The preparation of commercial bisphenolic compounds typically involves a distillation step whereby a purified bisphenolic compound is recovered and a residual bisphenolic stillbottom is separated from the recovered product. The bisphenolic stillbottom may also be described as a distillation residue. As is known in the art, the bisphenolic stillbottom exhibits different chemical properties, including reactivity, as compared to the remainder of the feedstock representing the purified products. Bisphenolic stillbottoms useful in the process of the present invention may include bisphenol A stillbottoms. It is generally known in the art that bisphenol A has a purity of at least 98%, on a weight basis and that bisphenol A stillbottoms are of a lesser purity. As noted above, it is also known in the art that bisphenolic stillbottoms exhibit different chemical properties, including reactivity, than bisphenol A, for example.
Bisphenol A stillbottoms are commercially available. One source for such stillbottoms is General Electric Company, Plastics Group, Schenectady, N.Y., under the trade name V-390 PHENOLIC EXTENDER (xe2x80x9cV-390xe2x80x9d). V-390 is a mixture of products produced during the manufacture of bisphenol A. V-390 is also known under the synonyms and trade name: BPA tar, BPA isomers, and LE 390 PHENOLIC EXTENDER. V-390 has a melting point range of from about 62xc2x0 C. to about 110xc2x0 C. (about 144xc2x0 F. to about 230xc2x0 F.).
An alternate source for Bisphenol A stillbottoms is Aristech Chemical Corporation, Pittsburgh, Pa. under the product name BPA HEAVIES. BPA HEAVIES is a mixture of Bisphenol A, o,p-Bisphenol A isomers, and phenol. BPA HEAVIES is also known under the synonyms: 4,4xe2x80x2-Isopropylidenediphenol, and Bisphenol A bottoms. BPA HEAVIES begin to melt at about 62xc2x0 C. (about 144xc2x0 F.).
Table 1, provided below, characterizes a typical bisphenolic stillbottom composition the composition of the present invention.
The percentages listed in Table 1 are on a weight-per-weight (w/w) basis calculated on the total weight of the bisphenolic stillbottom. It is understood that the component amounts will add up to 100 percent. It should also be evident from the data of table 1, that the bisphenolic stillbottoms of the present invention may contain substantially non-bisphenol A components.
In contrast to the biphenolic stillbottoms of the present invention, bisphenol A melts at 150-155xc2x0 C. Thus, it can be seen that the composition of bisphenolic stillbottoms, as used herein, is significantly different from the purified bisphenol product from which the bisphenolic stillbottom is separated.
The present invention provides a composition that is substantially lower in cost than bisphenol A. Because the composition of the present invention is a stable, single-phase, composition, it is readily used in the synthesis of resins, in place of bisphenol A, as illustrated by the following examples.
In one embodiment, the bisphenolic stillbottoms are first brought to a molten state. This is accomplished in a vessel to which heat may be applied. Once the bisphenolic stillbottoms are in a molten state water is then added to the vessel containing the molten bisphenolic stillbottoms. The weight of water added to the vessel is from about 1% to about 20% based on the combined weight of water and bisphenolic stillbottoms. Because the temperature of the molten bisphenolic stillbottoms may be near or above 100xc2x0 C., the atmospheric boiling point of water, it is preferred that the vessel containing the molten stillbottoms be so equipped to reflux the water vapor that may evolve from the vessel. The water and the molten bisphenolic stillbottoms are then mixed, for about 30 minutes to about 120 minutes, until a single-phase solution is formed.
In a preferred embodiment, the bisphenolic stillbottoms are heated to about 110xc2x0 C. and water is slowly added, under mixing, over about 15 to 30 minutes. The temperature of the resulting solution is allowed to drop to about 80 to 90xc2x0 C.
A typical mixing process is described as follows. Components, including the bisphenolic stillbottoms and water, are introduced into a 1 liter four-necked round-bottom flask. The flask is fitted with means to stir the flask contents, means to monitor the temperature of the flask contents, and means to reflux volatile components and products. Reflux is typically afforded by use of a reflux condenser fitted to one opening of the four-necked flask. The condenser is typically cooled using water. Components are pre-weighed before addition to the four-necked flask. The flask contents are heated by an electric heating mantle that is controlled by a rheostat, or by use of a steam table so that specific temperatures may be reached and maintained. Other arrangements will be known to those skilled in the art.
Different diluents have been studied for use in preparing solutions of bisphenolic stillbottoms. Table 2, below, provides data on experiments conducted to determine the compatibility of such diluents. Also included is stability information in terms of the temperature and amount of time over which the solutions were held.
In a further study of the compatibility of bisphenolic stillbottoms with various solvents, the data of table 3, below, was collected. In these tests, the bisphenolic stillbottom was heated to about 90 to 110xc2x0 C. and the diluent was then slowly added, under mixing, over a 5 to 10 minute period of time. Mixing was continued for one hour and the solutions were allowed to cool to room temperature. The number of phases exhibited were observed both at the elevated temperatures and at room temperature.
All of the solutions studied appeared homogeneous under mixing. Solutions a, c, e, g, and i exhibited homogeneity at both the elevated temperatures (90xc2x0 C.-100xc2x0 C. ) and at room temperature. Solutions b, d, f, and h showed exhibited homogeneity at the elevated temperatures but showed separation into two phases upon standing and cooling to room temperature.
Certain analytical tests may be employed to characterize the stable compositions of the present invention. These tests are described below.
Aqueous solutions of bisphenolic stillbottoms were tested for viscosity. Viscosity was determined using the well known cone and plate viscosity method. The cone and plate viscosity is a high shear viscosity that may be measured on a viscometer such as the Brookfield cone and plate viscometer, model 2000H. The Cone and Plate viscometer provides viscosity measurements of small samples utilizing a thermostatically controlled fixed flat plate and a rotating cone. Typically, values measured by the viscometer are converted into centipoise. The cone and plate viscosity results reported below were made at a temperature of 75xc2x0 C.
The water content of the stable aqueous solutions of the present invention were determined using the standard test method for water by the well known Karl-Fischer titration. This method uses Karl-Fischer reagent which is suitable for determining free water and water of hydration in most solid or liquid organic compositions and for a wide range of concentrations (i.e. from a parts per million order of concentration to pure water). This method is also known under the American Standard for Testing Materials method ASTM E 203-86.
The following examples serve to illustrate one embodiment of the present invention.